In addition to the sources of pollution of the atmosphere which we have been considering, there are various trades and manufactures in which poisonous matters are given off. Some of these are of an organic nature, as in the melting of fats, in the making of size and glue, in the boiling of oil, in the boiling of bones, and in many other processes carried out on a considerable scale, where the emanations are highly offensive and often of unknown chemical composition. Gas works must be included in this poisonous group, owing to the accidental escape of gas, sometimes in large quantity. In lime kilns enormous volumes of carbonic acid gas are poured out, both from the limestone burnt and from the fuel employed, and in this way persons living in the immediate neighborhood have been suffocated. In chloride of lime (bleaching powder) manufactories, and in places where it is used for bleaching wool and other materials, chlorine gas is given off into the air, causing when inhaled a great amount of irritation in the air passages. Moreover, this chlorine vapor is often carried in the air for long distances. In other branches of industry the workers are exposed to the vapors of sulphurous acid and muriatic acid, both of these being very irritating, and giving rise to various diseases of the lungs and eyes. Such, then, are a few of the impurities, more or less poisonous, to be met with in the air we breathe; and dangerous to health as all of them are, it must be admitted that they do far less mischief to the public health than the continual mismanagement of our atmospheric food, common in all classes of society, by which it is rendered unfit to support a healthy life. The two ways in which air may be rendered thus comparatively valueless are either by excluding it too much from our dwellings, and this is the fault of the rich, or by crowding too many people together in small rooms, and this is the fault of the poor. In the houses of the better classes the air is kept out by closed windows, doors, curtains, and even in some places by putting screens before the fire-places in summer, and in bedrooms in winter when fire is not used. Pure air is, in fact, the most important of all health factors. When it is breathed freely, plentifully, and continually, there are few diseases which it will not enable the body to resist. Nay, even some injuries, which, received by the denizens of the overcrowded city, would be speedily followed by death, will be readily recovered from by the agricultural laborer or country farmer, who, always breathing a pure atmosphere, has thus stored up a great amount of additional constitutional force.—_Good Words._ MANNER. By LORD CHESTERFIELD to his Son.